Because of the limited prognosis with massive PE, patients cannot provide informed consent to participate in this compassionate use protocol. Initially, written informed consent will be obtained from a physician not involved in the compassionate use protocol. Physician investigators will obtain written informed consent in all patients after completion of the PE catheter thrombectomy if the patient is consentable. The patient will be asked to participate in study-related procedures, including the measurement of plasma free hemoglobin from blood obtained during the procedure, echocardiography 24-72 hours after the procedure, and a telephone interview 3-6 months after the procedure.